* {
  margin: 0;
  padding: 0;
}
.header {
  height: 100px;
  background-color: #008000;
}
.header h1 {
  font-weight: 700;
  font-size: 26px;
  color: #00f;
}
.footer {
  background: #ffc0cb;
  height: 100px;
}
main {
  display: flex;
}
nav,
div,
aside {
  height: 500px;
  width: 200px;
  background-color: #ff0;
}
nav {
  background-color: #808080;
}
aside {
  background-color: #f00;
}
div {
  width: calc(100% - 400px);
}
